Not All Joints Are Flexible – #365papers – 2017 – 89

#365papers for March 30, 2017

Bailleul and Holliday, 2017, Joint histology in Alligator mississippiensis challenges the identification of synovial joints in fossil archosaurs and inferences of cranial kinesis: Proceedings of the Royal Society B, v. 284: 20170038

What’s it about?

In the past, when paleontologists have observed joints between bones, especially in the skull, that possess smooth surfaces, an assumption as been made that these joints are flexible. Flexible joints in the skull result in cranial kinesis, where the head can be deformed as exemplified by modern snakes as they consume prey much larger than their own heads. The authors show, through study of modern alligator skulls, that smooth joint surfaces don’t necessarily mean that a joint was movable, and that detailed study of the structure of the bone itself is needed to know if a joint could bend or not.

Why does it matter?

Some authors claim that cranial kinesis was present in certain dinosaurs, based upon the structure of some joints in the skull. These interpretations may be completely wrong, and must be tested using study of the structure of the bones around the joints.

Why did I read this?

Can I just say that it sounded interesting? Seriously, though, my life is rather mammal-centric, and I’ve always been fascinated by animals that could distort their heads to eat. This is cool.